The student will 1. observe the external obscertainer (these are sealed containers that come with the Lab Aids #100 kit). 2. make hypothesis on internal structure of several obscertainers. 3. retest each hypothesis. 4. check observation again, correct internal structure on each. 5. develop an appreciation of indirect observation and make the connection between this activity and the historical determination of the molecular structure of matter.

1. Instruct the students not to open the containers. 2. Tell the students that each container has one (1) steel ball inside each container. They may have none to several internal wall structure(s). 3. Demonstrate the possible internal wall structure on the board. 4. Give each student four (4) obscertainers. Instruct them to move the steel ball around carefully by shaking and tilting the obsertainer. 5. Ask students to make a guess about the internal structure of each obcertainer and to draw this structure on their worksheet. 6. Note that the first guess is called a hypothesis. 7. Tell the students to re-examine each obcertainer and make a second guess about its structure. Draw each second guess next to the hypothesis drawing. Call this second guess the "retest". 8. Discuss how much information could be obtained without actually looking inside. 9. Make a connection between this activity and scientist trying to determine the structure of molecules and atoms too small to be seen.

References:

Lab-Aids kits can be purchased from the following scientific supply houses: Central Scientific Company; Fisher Scientific; Wards Biology Supply. All three companies will furnish catalogues upon request.